spf fail error.

I am never new to this one so i am using dyndns and i get an spf fail error on some mail provider.
I'm using
v=spf1 mx ip4:100.000.00.000 mx:myserver.my.com mx:mx2.mailhop.org a:mho-03-ewr.mailhop.org -all
What i get is:
The result of the test (this should be the default result of your record) was, ambiguous . The explanation returned was, SPF Ambiguity Warning: No MX records found for mx mechanism: mho-03-ewr.mailhop.org.
So does anyone know a fix, or where should i ask this question?
Thanks.